The present invention relates to a photographic printing machine, and more exactly an apparatus by means of which both photographic images and digitally encoded images can be printed on light-sensitive paper. The art field of photography embraces printing machines by which images are projected from film onto discrete strips of light-sensitive paper. The exposed paper then passes through a succession of chemical treatment baths to be developed, and thereafter into a drying chamber, whereupon the finished photographs are ejected from the machine automatically.
Devices have also been developed for the printing of digitally encoded images obtained with video cameras or generated using computer graphics or other conventional systems and recorded on convenient storage media such as magnetic tape or magnetic or optical disk, typically the familiar CD. The digital information is relayed by a suitable electronic processor to a cathode ray tube, and the entire image reproduced and projected by means of appropriate optical devices onto the light-sensitive paper, which is then processed in the traditional way. Conventional systems for reproducing digitally encoded images normally make use of black-and-white cathode ray tubes which, in order to generate the full image, must project a succession of three primary black and white images. These monochrome images are the product of a previous filtering operation executed optically or electronically in the three primary colors, and must be reconverted when projected onto the light-sensitive paper with the corresponding colored filters, suitably piloted and controlled in conjunction with the relative exposure times by an electronic processor.
U.S. Pat. No. 4,742,375 discloses a solution in which the optical and electronic printing units in question can be either embodied separately and thus applied individually to a basic unit for developing the light-sensitive paper, or incorporated together with the developing unit into one assembly to create a single combination machine. Recent years have also witnessed the appearance of a special one-line cathode ray tube which, instead of generating a full raster image comprising a plurality of transverse lines in the manner of a flared cathode ray tube, emits a single transverse line of the image ensuring exact reproduction of the relative colors and impacting directly on the light-sensitive paper. Thus, by traversing the light-sensitive paper gradually over the light-emitting slot of the one-line cathode ray tube, it becomes possible to obtain progressive transfer of a plurality of lines, generated directly, i.e. without the use of other projection devices and without filtering in the three primary colors, which ultimately combine to make up the full image. Naturally enough, the system will also include suitable devices and means for controlling and coordinating the line-by-line output of the cathode ray tube and the movement of the light-sensitive paper feed mechanism, with the end of ensuring that a correct final image is obtained.
The prior art now encompasses a photographic printing machine equipped with this one-line type of cathode ray tube, though such a machine will produce prints only from digitally encoded images.
Whilst the patented machine disclosed in the aforementioned U.S. Pat. No. 4,742,375 affords certain advantages, insofar as the reproduction of photographic images both from film and from digital sources is performed by a single unit, it is nevertheless significantly complex in embodiment and therefore costly, given the need for two distinct units: one for the projection of images from film, and another for the projection of digitally encoded images. Moreover, the unit by which digitally encoded images are reproduced requires a relative optical projection assembly comprising a lens, together with the set of three colored filters, and therefore the various means and devices for controlling and coordinating the system overall, and also the conventional black-and-white cathode ray tube utilized, are of not inconsiderable dimensions. Generally considered, therefore, the machine is notably complex and costly, and discernibly cumbersome.